IDENTIFICATION AND DISTRIBUTION OF LARGES MASSES OF WATER IN THE LABRADOR SEA AND THE IRMINGER SEA

The main deep water masses present at the time of the CSS Hudson cruis es in Labrador and Irminger seas in June 1990 and October-November 199 1 have been identified using characteristic temperatures (T) and salin ities (S). The purpose of this study was to establish the transfer fun ctions between micropaleontological assemblages of top sediments and t hermohaline characteristics of water masses. The water mass at the top of the Labrador Sea (Labrador Sea Water, LSW) is formed after intense movements of winter convection in the first 900-m depth of the water column. Below that depth, the LSW parameters reach a double minimum (S almost-equal-to 34.80 and T almost-equal-to 2.9-degrees-C). Only the sediments located on the continental slopes of Greenland and Labrador between depths of 500 and 1500 m are in contact with the LSW. Below th e LSW, the superior fraction of the North East Atlantic Deep Water (NE ADW1) is characterized by a temperature maximum (almost-equal-to 3.3-d egrees-C) and, as such, is distinguishable from the inferior fraction (NEADW2). The latter is characterized by a maximum S (almost-equal-to 34,90) when compared with other intermediary and deep water masses. In contrast to the NEADW1 that freely circulates over the Reykjanes Ridg e, the NEADW2 must flow through the Charlie Gibbs Fracture Zone to go from the northeastern Atlantic to the Irminger Sea. The NEADW 1 and 2 respectively bathe the ridge section less than 2000 m deep and the Eur opean abyssal basins, On the contrary, the majority of the deep sedime nts of the Labrador and Irminger seas are in contact with the cold (T < 2.6-degrees-C) and salty (almost-equal-to 34.85) Denmark Strait Over flow Water. Although this water mass is normally found at depths excee ding 2700 m in pelagic environments, it can be found at less than 2000 -m depth on the bottom of the continental slopes of Greenland and Labr ador, where it is carried by the strong Deep Northern Boundary Current and Western Boundary Undercurrent. The presence of the NEADW 1 and 2 on the sediments is then restricted to narrow bands on the same contin ental slopes, between depths of 1800 and 2200 m.